Washington: Astronaut Scott Kelly, who has the distinction of having spent a year in the space, has said that the level of pollution in China and India is shocking.
"Seeing places like China and India, and the pollution that exists there almost all the time is quite shocking," Mr Kelly said in a brief media appearance with US President Barack Obama in the Oval Office of the White House on Friday.
"There was one day last summer, the summer of 2015, when I was in space I saw the eastern side of China was perfectly clear. And I'd never seen that before in all of my time in space, and I'd spent well over a year in space, total, at that point," he said.
"I could see all these cities that are - there's like over 200 cities in that part of China, with over a million people. And it was at dusk, and I could just, for the very first time, I was able to see them, and it was quite shocking," he added.
"I didn't really understand it until the next day I heard that the Chinese government had turned off a lot of the coal-producing power plants, stopped the cars from running in that part of the country for this national holiday, and the sky had completely cleared," Mr Kelly said.
"So it's interesting to see just how much of a negative impact we have on the environment, but also how quickly we can have a positive impact on it if we decide not to mention the atmosphere is very, very thin and scary-looking when you see it from space," he said.
Describing him as an American hero, President Obama said a while back, Mr Kelly completed what was the longest period of time that any US astronaut has ever spent in space -- almost a year. "What made this so important was not just to break a record, it gave us an opportunity to learn how Scott, as an astronaut, is impacted by lengthy stay like that. And we've got somebody to compare him to -- his twin brother Mark, also an astronaut," he said.
"So as a consequence, what we were able to learn is how does the body adapt, what kinds of physiological impacts -- psychologically, from what I understand from Scott, he was pretty good. But all this allows us to start thinking about long-term manned space flight," he said.
President Obama said the next American goal is to get to Mars. "Obviously, we've got a lot of work to do technologically to figure out how to get there, what kinds of space crafts allows us to do that most effectively," he said.
"But if we're going to do a manned flight, then one of the keys is making sure that our astronauts who are going out into space for that long period of time are also then able to come back -- what kinds of environments do we need to create for them, what are the biological sciences, and other elements that will allow for a successful mission," he added.